Skin and de-seed the grapes.
Insert a walnut of butter and 4 to 7 grapes inside each grouse.
Smear the rest of the butter all over the birds, and lay the rashers of bacon over the breasts.
Place on a rack in a roasting tin and cook in the preheated oven for 20 minutes.
Pour the warmed port over the birds and continue roasting for another 10 minutes, basting several times.
Put the remaining grapes in the oven to warm.
Remove the birds, and discard bacon.
Cut each bird in half and lay cut-side down on a slice of fried bread.
Reduce liquor in the roasting tin by rapid boiling; check seasoning and pour over the birds.